The Congressional Research Service has released two reports to answer this question:
- Staff Tenure In Selected Positions In House Members Offices 2006-2016
- Staff Tenure In Selected Positions In Senators' Offices 2006-2016
Interestingly, these analyses do not show tenure in position decreasing during this period. Senate staffers more often than not had lengthening tenures. House staffers' time-in-position tend to stay the same. Click the hyperlinked reports above to see all the nuances of the research findings.